|ORIGINAL SCIENTIFIC PAPERS|
|Pernar, N., Vukelić, J., Bakšić, D., Baričević, D.||UDK 630* 114.4 + 188|
|An Insight Into Genesis and Properties of Soil in the Riparian Region of North-Eastern Baranja pdf HR EN||223|
|Krpan, A. P. B., Poršinsky, T.||UDK 630* 363|
|Efficiency of Mechanical Felling and Processing in Soft and Hardwood broadleaved stands – Part 2: Efficiency of harvesters in the culture of soft broadleaf trees pdf HR EN||233|
|Zečić, Ž., Krpan, A. P. B., Poršinsky, T., Šušnjar, M.||UDK 630* 375|
|Efficiency of tractors 8090 and 9078 in shelterwood fellings of stands in Požega mountains pdf HR EN||245|
|Pilaš, I., Potočić, N.||UDK 630* 561 + 116|
|Depedence of intraseasonal variations of tree stem diameter changes, electrical resistanee of cambial zone and groundwater in common oak stand (Q. robur L.) pdf HR EN||255|
|Popijač, M., Seletković, I., Volner, M., Lovrenčić, I., Barišić, D., Kezić, N.||UDK 630* 160 + 161|
|Dynamics of 137Cs and 40K Movement in Silver fir Trees on Sljeme Mountain pdf HR EN||269|
|Summary: Cesium 137, or 137Cs, appeared in the atmosphere after thermonuclear tests were conducted intensively during the 1950’s and 1960’s, and the last large quantity of 137Cs was released after the major explosion at Chernobyl, when varying amounts of cesium deposits on the earth’s surface were observed. Irradiation was relatively brief, while levels of radioactivity were not equal, because they were linked to the amount of precipitation that appeared uncontrollably as a result of the explosion. Cesium very quickly entered the soil, but it only migrated to deeper layers very slowly due to the effects of surface waters (Filipović et al, 1991). The speed of cesium migration was slowed by radiation absorption processes. A relatively large quantity of clay and micro-minerals resulted in the fast and irreversible bonding of cesium with the soil (Cremers et al, 1988).Plant species are good indicators of cesium, even though their physiological characteristics may vary. This primarily depends on the free cesium in the root system that the plants have taken in from the soil and the extent of its penetration into the plant. Today it is important to stress that the physiological properties of plants and trees must be observed in light of new damage to forests caused by atmospheric pollution which is manifested in three different ways: a) through the direct impact of atmospheric pollutants on leaves and assimilation, b) by intake of substances into the soil by dry or wet deposition and its impact on physiological processes in subsoil and external portions of forest trees, and c) by indirect damage due to climate change and increased sensitivity of trees to extreme climatic, edaphic and biotic conditions. The level of radioactivity that contaminated the Republic of Croatia in the form of radioactive fallout has been estimated at 5.2 x 1015 Bq, which is approximately 0.28 % of the total activity released from the reactor at Chernobyl. Cesium behaves and is distributed in an organism in a manner similar to potassium (Baratta, 1994). The speed of cesium’s vertical migration in uncultivated soil depends on several factors, such as soil type, its mineral composition, pH, organic matter content, hydrogeological processes, and geochemical processes. On the forest floor, the primary source of 137Cs is the surface organic layer (Kruyts, Delvaux, 2002). Plants take in microconstituents, including radionuclides, in two ways: indirectly through their roots from the soil, and directly by sedimentation of radionuclides on leaves or flowers.|
Out of all potassium isotopes, only potassium -40, or 40K, is radioactive, i.e. it is a naturally-occurring primordial radionuclide with a half-life of 1.26 x 109 years. 40K is one of the most widespread natural radioactive elements, as it accounts for approximately 1 % of the total number of all atoms formed in the earth’s crust and its activity is easily and reliably measured.
In this research we want to contribute to knowledge of the dynamics of movement and the fate of model pollution of forest ecosystems, so the movement of 137Cs and 40K on various parts of silver fir trees (Abies alba) on the slopes of Sljeme was analyzed for the period from 1997 to 1999. Apex tips, or needles, bark and heartwood from the silver fir were taken as samples. 137Cs and 40K activity were established using the gamma-spectrometry method. In all samples analyzed, 40K and 137Cs activity had crossed into the apex tips and young needles. Increase in 137Cs and 40K activity in fir needles from the older to the younger apex sections did not exhibit a linear trend. We compared the dynamic of 137Cs and 40K movement in the needles, bark and heartwood by month in each of the three years. The 137Cs and 40K activity trend is increasing from older to younger sections in all parts. Similarly, we can say that activity is greatest in the tree bark in comparison to other tested samples. In each month in 1997, 1998 and 1999 (twelve months per year), the movement of cesium and potassium in the fir trees on Sljeme Mountain was measured. Samples of needles, bark and heartwood were always taken from the same trees.
The results presented indicate the importance of monitoring 137Cs dynamics, because this research shows and confirms that the cesium recorded after Chernobyl is still in the ecosystem. This model of the dynamics of movement 137Cs and the link between this movement in relation to the physiological functions of the trees have facilitated more clear and accurate monitoring of other negative consequences which occur in forest ecosystems and have a negative impact on the development of trees, in this case the silver fir.
|Posavec, S.||UDK 630* 652|
|Specificy of Bussines Analyses Entities in Managing with Forest and Forest Land pdf HR EN||279|
|Štorga, D.||UDK 630* 582 + 525|
|Application of GIS in Stand Extraction According to Dendrometric Parameters pdf HR EN||287|